1. Field of the Invention
The present invention relates to an electrode having a current collector and a composite mixture layer to which a composite mixture including one of a cathode active material and an anode active material is applied and a method for manufacturing the electrode, and more particularly to an electrode having a new electrode form and a method for manufacturing the electrode.
2. Description of the Related Art
As cordless and portable electronic devices have been increasingly developed, batteries employed as power sources for driving various types of electronic devices, especially, secondary batteries have been demanded to be compact and light. For these electronic devices, there have been used nickel-cadmium secondary batteries, lead-acid batteries and nonaqueous electrolyte batteries using active materials capable of doping with and dedoped from lithium, what is called, lithium type batteries.
Particularly, the lithium type batteries such as lithium batteries or lithium-ion batteries have advantages, among these batteries, that they are high in their battery voltage, energy density, low in their self-discharge and excellent in their cyclic characteristics. Accordingly, these lithium type batteries have been used as practical and commercial batteries.
In recent years, it has been necessary for the lithium type batteries to have battery forms adapted to the forms of the electronic devices. The lithium type batteries need to have, for example, forms of sheets or forms of strips so that they can be mounted on the electronic devices such as hardwares.
Since liquid type batteries using nonaqueous electrolyte solution as electrolytes employ metallic cans as outer jacket materials in order to prevent the leakage of liquid and ensure a safety, the forms of the batteries cannot be changed. Therefore, it is difficult to adapt the forms of the liquid type batteries to the forms of the electronic devices, and, the batteries having, for example, the shapes of sheets or the shapes of strips cannot be realized.
Thus, solid electrolyte batteries using solid electrolytes in which there is no fear that liquid as the electrolyte leaks and laminate films or the like are used as the outer jacket materials are put to practical use. Since the solid electrolytes and the laminate films used for the outer jacket materials are excellent in their flexibility, the solid electrolyte batteries having the solid electrolytes and the laminate films are also excellent in their flexibility. The batteries can be relatively easily formed into the shapes of sheets or the shapes of strips.
When the multi-function of the hardware is taken into consideration, the battery needs to have a high capacity, so that the area of the electrode having the composite mixture layer and the current collector needs to be widely and adequately ensured. When the electrode has a single-layer structure, a wide electrode area is required in order to achieve a desired battery capacity. Further, for the outer jacket of the battery, an area equal to or more than the area of the electrode is necessary. Accordingly, when the area of the electrode is increased in the electrode having the single-layer structure, the uses thereof are inconveniently restricted and a manufacture cost is disadvantageously increased. Thus, there is made a proposal that an electrode has a multi-layer structure by forming a composite mixture layer and laminating, for instance, a rectangular current collector to ensure a wide electrode area and achieve a desired battery capacity and make an external form of the battery compact.
However, when the electrode has the multi-layer structure by laminating the current collectors, it is necessary to pull out leads respectively from the current collectors upon manufacturing the electrode, so that a volume energy density is decreased for the leads. Accordingly, it is inconveniently difficult to more increase a high capacity.
Further, when the electrode has the multi-layer structure, since various kinds of steps such as cutting a lead for each current collector and welding and connecting the lead are required, there exist problems that a manufacture cost is high, much labors and time are required for producing the battery and a productivity is not good.